Fluid pressure intensifying means



5 sheets-snee: 1

E. A. ROCKWELL FLUID PRESSURE INTENSIFYING MEANS July 28, 1953 FiledJan. 25. 1947-' July 28, 1953 E. A. RocKwl-:LL

FLUID PRESSURE INTENSIFYING MEANS 5 Sheets-Sheet 2 Filed Jan. 25. 1947TlrzIJL. f /00 95 55 i |NvEN`ToR fon/Aena Ran/WELL.

July 28, 1953 Filed Jan. 25. 1947 E. A. RocKwELL 2,646,665

FLUID PRESSURE INTENSIFYING MEANS 5 Sheetsheet 5 July 28, 1953 E. A.RocKwl-:LL 2,646,565

FLUID PRESSURE INTENSIFYING MEANS Filed Jan. 25. 1947 5 sheets-sheet 4July 28, 1953 A E. A. RocKwr-:LL 2,646,665

FLUID PRESSURE INTENSIFYING MEANS 5 Sheets-Sheet 5 'T1 :,l.

Filed Jan. 25.194'7 INVENTOR ATTORNE fondeo Aacrmea.

Patented July 28, 1953 UNITED S'iATES PATE.

GFFICE 25 Claims. l

My invention relates particularly to power units which are adapted todeliver power for work performance generally, but which, also, havespecial application for the delivery of power for the operation ofautomotive vehicle accessories, as for instance 4automobile brakes.

The object of my invention is to provide an improved form of power unit,by means of which the desired amount of power may be delivered fmoreeiectively and with a simpler construe "tion Another object is to obtainin the vsame or'm of power unit, and by the substitution of 'differentelements therein, any desired boost ratio of input and output pressure,not limited to a fixed ratio therefore, and by means of which,furthermore, any required pedal pressures may be obtained as well as anydesired output pressures. A further object is to provide lightness ofconstruction by reason of the concentric arrangement of the parts, whichbalances a central control plunger, with consequentsaving of materialand labor in the construction of the power units. This also permitsself-alignment of the movable parts of the power unit. Another object isto provide an effective control owing to the fact that in my power unitthe whole piston area determines the lap position of the valves 'andconsequently enables a fast movement of the 'parts to be attained. Afurther object is to provide an effective regulating inlet and outlet'valve means. xStill a further object is to provide 'an effective valveof this character by which the presence of an excessive pressure isprevented owing to the unseating of the air inlet valve when a vacuumgreater than desired is applied thereto. Still another object is toprovide an effective reaction means, the force or ratio of which may bereadily changed by substitution of springs or otherwise, to control thereaction or feel applied to the pedal. Another object is to provide aselective set of springs so that by inserting springs of differentdimensions or tensions, different boost ratios, different valveunseating positions and reaction forces may be attained.

A special purpose of this invention is to provide a unit which isadaptable to be made in a complete range of sizes from the smallest tothe largest trucks and one that will be readily adaptable to an requiredpedal ratio to .the master cylinder. Previously, in order to accomplishthe :adjustment of the ratio, it has been necessary to :select either aspecial size control plunger or to fchange a leverage ratio connectingthe plunger -'and the valve in the power unit. In order that the parteai unit `can bestandardizerl .se to produce a maximum of interchangeableparts at a minimum cost, in this invention it is necessary to changeonly the rate of a spring.

A further object of this invention is to provide a control plungerhaving an air inlet at one end thereof and an elastic grommet valvedirect ly cooperating with the end of the plunger 'so as rst to close avacuum valve and subsequently open an air passage through the center ofthe plunger. lrIhis direct action eliminates the lever' arrangementpreviously used, avoids the use of a seal and permits a slightmisaligment f the vacuum. piston with respect to the power plunger to bepresent.

A further purpose of the invention is to provide a very early cut-inpoint for the unit, so that the power will start to be applied almostinstantaneously with the application of the pedal.

Another object is to provide a unit wherein the boost ratio may berelatively low so as to permit manual boosting `pressures to be appliedduring the power effort.

A further object is to provide a control wherein the whole area of thepressure responsive pow-k er piston, operating against a spring plate,will be effective to determine the lap position of the control valveaccording to the rate of deection of the plate. It also is a purpose totransmit this force through the spring plate directly to a plurality ofpower plungers equally and symmetrically spaced.

It is a further object to have a spring return for the control plunger,reacting against the power plunger or plungers so that the manual forcewill act through a spring selected to give the desired pedal pressurefor any given mechanical linkage arrangement to the pedal. It also is anobject to produce a very fast release of the brakes so as to avoid unduehysteresis in the on and off application of the brakes, that is to say,lag in coming off.

A further object is to provide a unit which can be manufactured verycheaply and one in which a single bleeder is used for both the controlplunger, as well as the power plunger or plungers.

A further object is in a simple construction-to use an aluminum pressurecylinder, having special types of seals which avoid the use of bushingsin the manufacture of the unit, thereby saving space and cost.

Another object is to provide a removable control cylinder which can bescrew-threaded into a pressure cylinder casting, and this cylinder canbe made of any desired material, such as cast iron pipe or other tubingwhich can be manufactured cheaply on a screw machine, there being nooutlets necessary to be added on the tubing itself.

Further objects of my invention will appear from the detaileddescription of the same hereinafter.

While my invention is capable of embodiment in many different forms, forthe purpose of illustration I have shown only certain forms thereof inthe accompanying drawings, in which- Fig. 1 is a vertical longitudinalsection of a power unit made in accordance with my invention, showingone form of grommet valve in its initial position, the section beingtaken on line l-l of Fig. 2;

Fig. 2 is an end elevation partly in section of the same;

Fig. 3 is a transverse vertical section showing the same constructionexcept that a modified form of plunger mounting of the reaction elementis shown which may be in the form of a star spring;

Fig. 4 is a fragmental vertical section of the said modified form o fpressure-increasing plung er therei-n;

Fig. 5 is a longitudinal vertical section of a modified form of grommetvalve that may be used;

Fig. 6 is a side elevation of the grommet valve shown in Fig. 5;

Fig. 7 is a longitudinal vertical section of modiiied inlet and outletvalves showing a valve body preferably made of metal, and havingcooperating therewith elastic valve seats, such as of rubber, etc.;

Fig. 8 is an end elevation partly in section of another modification ofthe power unit;

Fig. 9 is a transverse section thereof in its initial position, taken online 9 9 of Fig. 8;

Fig. 10 is a plan view of the same; and

Fig. l1 is a plan view of the reaction spring plate of Figs. 8 to 10.

Referring rst to Figs. l to 4 of the drawings, I have shown a mastercylinder I having a pedal 2 connected by a pipe 3 to an inlet opening ona power unit head 5 'which may be a light casting, if desired, such forexample as of aluminum or an aluminum alloy. The head 5 may be securedto a power unit casing i5 of sheet metal by means of rods with hooks 8on one end of each of the same, and screw-threaded ends 9, provided withnuts It, which pass through holes Il in the periphery of the head 5. Thecasing 6 may have secured to the same, if desired, a connection i2,screw-threaded to receive a plug i3, which may be removed and supplantedwith a connection to a trailer, if desired. Also, the head 5 has ascrew-threaded opening I4 connected by a pipe I5 to an automobile enginemanifold i6, or to any other source of vacuum.

The inlet s leads to an annular chamber I? in the head 5 adjacent to ascrew-threaded opening I8 having therein a screw-threaded end of amanual or control cylinder is which may be of iron or steel to providean internal cylindrical milled surface 2i! for the reciprocation thereinof a piston 2l located on a manual or control plunger 22 having alongitudinal air passageway 23 to convey air from an air inlet 2i. Thepiston 2l is held in place against a shoulder 25 on the plunger 22 bymeans of a split ring 26 in a recess 2 on the end of the control plunger22. Also, on the inner face of the piston 2i there is a seal of anydesired character, as for instance an elastic deformable ring of rubberor rubber substitute 28, located in a V-shaped recess 29. On the outsideof the piston 2| there is a low pressure seal in the form of a ring ofcircular @X955- section and which is of such a size that, initially, ithas a somewhat flat outer face by being forced into a V-shapcd retainerrecess 3l. This will provide an effective seal at all times against evenlow fluid pressures. Preferably, the said ring 30 is made of a rubber orsimilar material, which will tend to expand slightly under the influenceof the brake fluids present, as for instance a1- cohol, castor oil, etc.Adjacent to the seal 39 there is a high pressure seal 32 ofsubstantially the saine material as the ring 3d. The seal 32, which iscircular in cross-section is preferably of such a size that wheninserted in the cylinder t 9 it will contact only lightly with the innerface of the cylindrical chamber 2i@ and will leave initially and underlow pressures, a free passageway 33 beneath the seal 32 within aU-shaped recess 34. When higher hydraulic pressures are being applied inthe annular chamber il, low pressures will be prevented from leakage bythe seal 30 and high pressures will then be prevented from leakage bythe seating of the seal 32 tightly in flat position on its periphery andside. When the high pressures are released the high pressure seal 32will again relax to re-open the passageway 33 beneath the same toprevent trapping of the high pressure fluids between the seals 3Q and32. This construction of seals is the same as described in detail in mycopending applications upon Sealing Means, Ser. No. 729,931, ledFebruary 2l, 1947, now Patent No. 2,593,193, and Unit for DeliveringIntensied Power, Ser. No. 690,638, iled August l5, 1946. Also, aroundthe control plunger 22 there is a low pressure seal 35 in a V-shapedrecess 35 constructed like the low pressure seal 3!! and recess 3l, anda high pressure seal 3l in a U-shaped recess 38 constructed like thehigh pressure seal 32 and recess 33, except that in this instance theelastic deformable material of the seals 35 and 31' is preferably suchas to slightly contract under the iniluence of the said brake fluids,such for instance as neoprene. These seals are also made in the mannerdescribed in detail in the said two copending applications for LettersPatent.

When the brake iluid has been forced into the annular passageway Il bythe operation of the pedal 2, it will force the piston 2i to the right,thus releasing a cam surface on its periphery from a Fluted valve rod itwhich initially has been forced to the left in Fig. 2 by the cam 39 soas to allow the hydraulic brake fluid to pass from the annular chamberil through a valve seat M which has a valve member l2 secured to theiuted valve rod EB, said valve d2 being normally pressed against itsseat, when permitted by the cam 39, by a spring i3 carried in ascrew-threaded plug 44 in the head 5. When the liquid thus passesthrough the valve di, 42, it gains access to two connecting conduits 45and 9 which provide communication to three power cylinders 41, 48 and39. One end of the conduit d5 may be closed by a screw plug 59 and oneend of the conduit 46 may lead by a screw-threaded outlet 5| and a pipe52 to front wheel brake cylinders 53 and 54 and rear wheel brakesylinders and 5S. In this way, initially, the manual hydraulic pressuresapplied by the pedal il may pass directly to the wheel brakes 53, 54%,55 and 59 to set the brakes initially and apply a small amount ofbraking eiiort, if desired.

When, however, the hydraulic pressure from the pedal 2 is increased thecam 39 will be released from the valve rod thus closing the valve di, i2and moving the piston 2i to the right, in Fig. l,

so as to admit air through apertures 51 and 58 in a cap 59screw-threaded on the end of the control plunger 22 and thence past anannular valve seat 80 which normally rests on the inner face 8| of arubber grommet valve 62, and thence by radial openings 63 in the rubbergrommet valve 62 to the inside of the power unit casing 6 on the leftface of a power piston 04 which slides within said cylindrical casing 6.This rubber grommet 62 is forced towards the right, in Fig. 1, againstthe inlet valve seat 60 with the aid of a spring retaining cap 85 whichsupports a coil spring 66 around a stem 51 formed on the cap 59, thespring 06 being held in place by a cotter pin 68. It will also be notedthat the spring retaining cap 65 has spring arms 09 which are bentoutwardly and then inwardly to place a tension inwardly on the grommetvalve to aid in seating it and so as to overlie an inwardly andoutwardly7 directed nange 10 on the grommet |52. The said flange 10 hasan inwardly directed portion 1| fitting against the outer face of thecap 59 to form a seal therewith, and it has an outwardly directed ange12 which forms an outlet valve member seating against an outlet valveseat 13 on a plate 14 forming a part of the piston S0. The outlet valve12, 13 is initially held in open position to admit the vacuum receivedby the inlet I4 and at the right face of the plate 14 so as to beadmitted to the left face of the plate 14 in Fig. 1. This open positionof the outlet valve 12, 13 is brought about by reason of the presence ofa coil control and reaction spring 15 around the control plunger 22 andwhich rests against a ange 18 on the right-hand end of the cap 59. Therighthand end of the coil spring 15 is carried in an annular spring cup11 which is positioned on the control plunger 22 by a split retainingring 18 in a recess 19 in said plunger 22. The outer edge of said cup11, furthermore, is supported against a star reaction spring 80 havingspring fingers 8|, which are shown, also, in Fig. 3, and which restagainst the right face of the power piston plate 14. It will beunderstood that this spring 00, as well as the spring fingers 8|, alsothe spring 15, may have any desired strength or shape or tension inorder to provide the desired ratio of input and output force or boostratio requiring any desired input pressure and delivering any desiredoutput pressure, according to the needs of the installations and thatthese changes can be accomplished without the necessity of making anychanges in the design or construction of the other parts o the powerunit apparatus. Also fastened to the star spring 80 there are providedthree pressure increasing plungers 82, 83 and 84 which operate,respectively, in the pressure increasing chamber 48, 49 and 41. Theseplungers 82, 83 and 84 may be secured to the star spring 80 either bywelding or in any other desired manner, although for this purpose,referring to Figs. 3 and 4, instead, each of said plungersmay beprovided with a terminal flange 85 adjacent to a cylindrical stem 8Sforming a recess 81 around which the spring arms 8| pass for thispurpose, as shown in Fig. 4. Each of these plungers 82, 83 and 84,furthermore, may have a low pressure annular seal 88 and a V-shapedrecess 89 constructed like the seal 35 and recess 35. Also, it may havea high pressure seal 99 and a U-shaped recess 9| constructed like thehigh pressure seal 31 and recess 38. Furthermore, a conical retractingspring 92 is provided between the star spring 80 and the head 5 forreturning the power piston 64 to its initialposition. Centeringdowelpins 93, 94 and 95 pass into corresponding clongated recesses 96 inthesaid plungers 82, 83 andl 84, said dowel pins having near theirleft-hand ends hexagone 9.1 and 98 as well as washers 99 for fasteningthe centering dowel pins 93, 94 and to the power piston plate 14', andfor holding in position a seal retaining plate |00 which holds in place,around the periphery of the plate 14, a leather seal |0|. A feltlubricating ring |02 carrying a liquid lubricant may also be supportedagainst the seal retaining plate |00 by a disc |03 having an annularrecess |04 for the felt ring |02.

In Fig. 5 I have shown a slight modification of the grommet valve. Inthis instance I provide a grommet valve |05 of rubber or some otherelastic material, such as a rubber substitute, having a central airopening |00 through which projects a stem |01 mounted on a closed capbrazed to the end of the control plunger 22, said stem |01.

having a Cotter pin |08 for retaining a conical spring |09 against theupper face of a spring retaining cap ||0 having spring arms con-Astructed like the spring arms 0S, so as to be supported against atransverse flange i2 on the grommet the same as in the case of theflange 10 previously referred to. The spring |09 presses an inner edgeI3, forming an inlet valve element of the opening |00, into contact witha valve seat I 4 on the outer end of a control piston I5, like thecontrol piston 22, having a longitudinal airpassageway H5 leading tolateral air openings ||1 so as to communicate with an air chamber H8leading to the air valve ||3, H4. The stem |01 is connected to thecontrol piston l I5 by webs H9.

In Fig. 7 I have shown a slightly modied form of the inlet and outletvalves, comprising'a sleeve |20 of metal or other rigid material, havingat its upper end a iiange |2| tting within va U-shaped ring |22 ofrubber or rubber substitute,j having supported on the upper face.thereof a conical spring |23 held by a Cotter pin |24 on a `stem |25secured to a control piston |20 like thel control piston 22. The rubberring |22 has a central air passageway |21, a lower inner edge |28 ofWhich forms an air inlet valve element to cooperate with an air inletvalve seat |29 formed on the outer end of the control piston |25. Also,an air passageway |30 in the control piston |20 leads by openings 13| toan air chamber |32 on the inside of the sleeve |20 so that when theAvalve |28, |29 is unseated the air from the passageway |30 can pass intothe left-hand end oi? the power unit through the passageway |21. Thelower end of the sleeve |20 has a screw-thread |33 to receive a sealretaining ring |34 so as to clamp in position a leather seal |35 restingagainst the outside of the control plunger |26. Also, said ring 34 hasat its lower edge an outlet valve element |30 which cooperates with avalve.

seat |31 on a U-shaped ring |38, made of rubber or rubber substitute,which is carried by the power piston plate 14. Within the ring |38 thereis a central opening |39 for conveying, in the initial position of theparts, vacuum to both faces of the power piston 64'.

In Figs. 8 to 11 I have shown a further -modi-v `cation of the powerunit which'is constructed.

like the power unit in Fig. 1, but with a grommet valve like that shownin Figs. 5 and 6, ex-

cept as follows: In this instance there are pro-v |40 and |4| areconnected, respectively, *to 'pas-1.A

7 sageways |42 and |43, which lead to a valve chamber |44 having thereinan air bleeder screw |45 normally closed by a removable screw |46, saidscrew |45 being hollow, and having a port |41 leading to the valvechamber |44. in said chamber there is a helical spring |48 seated at oneend on a screw plug |4511 in the head and at its other end on a valverod |56 carrying a conical valve |5| adjacent to a valve stem |52passing through an opening |53 leading to the annular chamber |1 so thatthe stem |52 can be operated by the cam 39 to close oif said valve |44by seating it on its valve seat |54. The valve |44, |54 is open whenstarting to operate the power unit manually, but when further manualpressure is applied the valve |44, |55. is closed, and power pressurefrom the power cylinders |46 and |4| is thereafter applied to the brakesby power intensifying plungers |55 and |56. mounted on a star springplate having spring ngers 8| a, by passing therethrough and beingsecured thereto by means of split rings |51 carried on reducedextensions 56 of the plungers |55 and |56, through which extend thebolts 65 which eX- tend into the recesses 96. The ends of the plungers|55 and |56 also support in place a retaining ring |59 against the plate36, the latter being adjacent to a dished spring supporting plate |66around the control plunger. The dished plate 60 holds in position astrong control spring 16|, the tension rate of which is selected to givethe desired feel, one end oi which fits against a stop plate |62 whichis supported in position on the control plunger 22 by a split ring |63and guided by two headed fastening screws |64 on the plate 14. Thetension rate of the control spring |6| will allow the pedal to build upits force as the spring plate 86a is deflected, thus determining the lapposition of the vacuum and air valves. The stop plate |62 is heldagainst the split ring |63 by a small control spring |65 which is alsosupported by the dished plate |66 and and normally holds the vacuumvalve H2 o its seat. The spring |65 also acts to return the controlplunger 22 and to allow the valve |44 to open against any trappedpressure. Each headed bolt |64 is secured to the plate 14 by a nut |66and a lock washer |61. Spacing rings |62 hold the plates 14 and 62 apartso as to leave air ports |69 in the plate 14 uncovered by the plate |62.Also, the two screws |64 have screwthreaded ends which act as stops forthe maximum manual travel, thus permitting the application of additionalmanual pressure after the air valve at the ports |66 is completelyopened.

In the operation of my invention, referring first to Figs. 1 to 4, inthe initial position of the apparatus with the Vacuum being applied fromthe manifold I6, the piston 64 is initally vacuum suspended and theoutlet or vacuum valve 12, 13 will be in open position due to the actionof the coil spring 92 resting against the spring plate 86 which in turnsupports the spring by the ring 11, thus having the effect of freeingthe valve element 12 from the valve seat 13 as the spring fingers 8|have in this position no Contact or only a light contact with the plate14. When the manual pressure exerted by the pedal is conveyed by the lowpressure hydraulic liquid through the pipe 3, the said pressure will beconveyed into the annular chamber l1 and, as the cam 39 is in contactwith the iiuted valve stem 46, the valve 4|, 42 will be in open positionso that the pressure liquid is thus conveyed through passages 45 and 46to the three pressure-increasing These pressure intensifying plungersare chambers 48, 49 and 56 and thence by the outlet opening 5| to thewheel brake cylinders 53, 54, 55 and 56, so as to set the brakes and, ifdesired, apply a slight braking force to the wheel brakes. When thehydraulic pressure in the pipe 3 is, thereafter, increased by the pedal2 the cam 39 will move away from the valve rod 4|), thus seating thevalve 4|, 42 and cutting olf the manual hydraulic pressure to the wheelbrake cylinders 53, 54, 55 and 56. Simultaneously, however, with thismovement of the cam surface 39 to the right in Fig. l, the piston 2| isbeing moved to the right in Fig. 1 against the opposition of the controlspring 15. This results in the seating of the outlet valve 12, 13 so asto cut off the chamber at the left of the power piston 64 from thesource of vacuum |4. Upon further pressure being applied in the pipe 3,the air inlet valve 6|, 66 becomes unseated so as t0 admit air throughthe inlet valve 6|, 65, through the ports 63 to the left of the powerpiston 64. This moves the power piston 64 to the right against theopposition of the reaction spring fingers 3| which control the powerapplied to the cylinders 4l, 46 and 4S and, therefore, also the reactionexerted from said cylinders onto the pedal 2, which increasescoordinately as the power pressure applied at the left of the piston 64increases. These reaction spring ngers 8i not -only control the reactionto the pedal '2 according to the amount of power pressure being applied,but also convey the power pressure, due to the force of the air at theleft of the power piston 64, to the plurality of pressure-increasing orintensifying plungers 82, 83 and 84 which are balanced against eachother to prevent any torsional leverage action on the control piston 22,in applying the fiuid pressure from the cylinders fis, 4S and 56 throughthe pipe 52 to the wheel brake cylinders 53, 54, 55 and 56. The absenceof any such leverage makes a light construction feasible. Thus, thepower pressures applied by the cylinders 48, 49 and 58 are coordinatedto the reaction or feel on the pedal 2, but when the power is beingapplied, this is added to the manual force exerted, so that bothtogether apply the braking eifort which is coordinate to the reaction orfeel exerted on the pedal. However, when an increase of pressure in thecylinders 41, 48 and 46 is reached coordinate to the position of thepedal 2, the said pressure will act on the piston 64 to close the airinlet valve 66, 6|, until a further movement of the pedal 2 takes place.Accordingly, also, when the manual pressure is being released ordecreased in the pipe 3 the valve 12, 13 will be opened somewhat, afterseating the inlet valve 66, 6|, thus restoring the parts to theiroriginal position. Also, it will be understood that in the course of theoperation of the power unit in this manner, if, for instance, anexcessive vacuum should be present in the manifold i6 and, therefore, atthe left of the piston 64 in the power unit, this will unseat the rubbergrommet inlet valve 66 from the inlet valve seat 6| on the end of thecontrol plunger 62, thus admitting some air to the interior of the powerunit casing 6, at the left of the piston 64, which is thence conveyed bythe pipe l5 to the intake manifold of the automobile engine, thusdecreasing to that extent the consumption of gasoline in View of thevacuum decreased thereby.

By this means, furthermore, it wil1 be seen by substitution of othersprings or springs of diiferent sizes, lengths or tensions for thecontrol and reaction spring 15 with or without a substitution of othersprings of different designs andtensions for the reaction spring 82, theboost ratio .of the power unit can be readily changed as Well yand whichmay be made at a low cost, but which is adapted for securing a widerange of pressures and boosting ratios in the different installationsinto which it may be applied. It will also be understood that, as aboveindicated, a larger or -smaller number of the power cylinders 48, 49 and58 and intensifying plungers 82, 83 and 84 can be utilized instead ofthree such cylinders and plungers, but preferably in such a manner thatthe plurality of such cylinders and plungers will be balanced againstone another in order to avoid placing any torque or torsional strainupon the y manual plunger 22. This construction is, furthermore,advantageous for the reason that all of the input pressures react backon the pedal 2 in view of the fact that the entire area of the powerpiston 68 operates on the spring fingers 8| and thence onto the pedal 2.

The modied form of grommet in Figs. 5 and 6 operates in substantiallythe same manner as the grommet shown in the preceding iigures except inthis instance the air, instead of passing through the radial ports 63,passes through the single central port 186, and except that the airreaches the same by passing from the longitudinal passageway 1|6 throughlateral ports ||1 in the control plunger 1|5 instead of through thelongitudinal ports 56, in the preceding figures.

The modified form of valve construction in Fig. 7 operates insubstantially the same manner as that shown in Figs. 5 land 6. Thecourse of the air is the same in Fig. '1 as in the preceding iigures. Inthis instance, however, instead of having a rubber grommet, the metallicor rigid sleeve |26 admits the air past the rubber ring |28 which seatson the valve seat 129. Furthermore, instead, in this construction themetallic rigid sleeve 134 cooperates with the rubber outlet valve ringso as to withdraw the air through the outlet valve |36, 131. Besides, inthis instance there is the leather annular seal |25 which seals theinlet valve |28, |29 from the outlet valve |36, |31 instead of dependingupon the rubber grommet itself for establishing such seal.

The modication shown in Figs. 8 to 11 operates approximately as in Figs.1 to 6, but in this instance the spring |09 is just strong enough tohold the air inlet valve 66, 6| closed normally. Furthermore, it will benoted that the stop plate |62 cooperates with the plate 14 to limit thetravel of the control plunger, and in case of a very low vacuum thecontrol plunger 22 can apply 'force through the same onto the plungers|55 and 156, thus avoiding excessive loss of pedal force due tocompression of the spring |61;

It will be noticed, also, that the control of the unit introduces a wellmodulated travel, and vthat the exibility of this action gives a verysoft and rangy pedal feel, as the whole large piston area of the piston64 is used in acting on the ngers 8| as a control means, so that thereis no hesitancy or lag in the off brake control. It will be seenv thatVarious input and output ratios can readily be selected according topiston size and master cylinder'capacities land mechanical ratios,simply by selecting the springs in the desired ratio of their deflectionrate. The pedal pressure versus line pressure characteristics can bechanged by providing springs or any other suitable arrangement to givethe exact characteristie which might be required by various engineers,all this being accomplished without departing from the basicconstruction and the use of the same standard Darts. The single bleederscrew |46, mounted at the high point, also is desirable as the bleedingoperation on the production line can be accomplished more quickly.

Gne of the very important advantages of the present power unit is thatit avoids the relatively small areas and small forces in previous units,which determine the valving movement and reaction or feel produced onthe pedal. In the present unit, as illustrated, for example in Figs. 8to 1l, the direct feel reaction is at least 350 pounds of force, whichis nearly ten times that usually present in previous power units, and nobalancing of this pressure is necessary to hold a lap position of thevalve inasmuch as the reaction of the power piston for this purposeutilizes substantially the entire area of the power piston 64. Thevalve, therefore, can be closed by the power piston irrespective of anyselected pedal position in the control r-ange.

Also, the input and output ratios can be readily determined byspecifying the relative rates of the springs 81a, |6| and |65. Besides,an early power cut-in can be easily selected, accordingly, to obtain amaximum range of pedal pressures for a lgiven maximum brake linepressure.

The valve control provides an instantaneous and accurate pedal feel, bylarge and adequate directive force, by accumulating energy during thebrake operation.

Because of the large effective force applied, the valve operation is notsubject to sticking o-r delayed release'due to seal friction. 1

The power unit, furthermore, is advantageous as it can be made withsimplified pressure casting, stampings, springs, snaprings and screwmachine parts; also, inasmuch as the vacuum and air valves are combinedin a single rubber or synthetic rubber grommet, having a positive directfollow-up action. Also, the seals are of a new type, giving maximumeffectiveness and long life, with low friction. However, inasmuch as thesecondary control spring |6| is free from the pressure piston 64 therewill be a movement of the intensifying plungers |55 and |56 when them'astercylinder pressure overcomes the force of the primary controlspring |65. As this action proceeds the intensifying plungers |55 and|56 will move to act as theplate 14 by the fingers 8| to clo'se thevacuum ports |69. A further movement will just slightly crack open theair valve at the left hand end of the grommet |05 by the withdrawal. ofthe end of the plunger 22 from the inner face of the grommet 105. Atthis time the transition valve 15| is still slightly open and the piston14 is about ready to .contact the secondary control spring 16|.Now'that'the power has cut in at this low manual `pressure the pistonassembly 14 will move to the right and the pedal 2 will follow throughprogressively, increasing the pressure, if desired, the resistance ofthe control springs |65 and |61 being determined by the rate of thesesprings, which will determine the pedal pressurer range. The powerpiston 14, thus', will transmit the force produced by the modulatedpressure differential, through the finger springs Bla, directly to thehydraulic plungers |55 and |55, this force being added to the manualforce transmitted through the primary |65 and secondary |6| controlsprings, resulting in the boosted controlled brake line pressure. Sincethe power piston will have a slight movement, relative to the powerplungers, yas determined by the rate of the iinger springs, it will beapparent that for any holding or lap positioning of the valves at anypoint in the power range, there will be a measure of the force appliedto the piston due to the differential across the power piston, and itwill be balanced against the nger springs. It is apparent that withthese accumulated large forces determining the valving events that therewill be instantaneous release and follow up.

Upon a release of the pressure on the pedal 2,

the air Valve on the grommet will remain closed, and the control springs[6| and E85 will instantly retract the control plunger 2| and open thevacuum passages |59 so as to produce a lower differential of pressureacross the piston 'I4 and thereby effect any desired release. 'Ilhefinger Springs Bla will instantly balance this pressure, the vacuumvalve passages |69 will shut off, and the unit will hold this particularpressure on the release until some further alteration or release of thepressure is effected by the pedal 2.

While I have described my invention above in detail I wish it to beunderstood that Amany changes may be made therein without departing fromthe spirit of the same.

I claim:

1. A power unit, comprising a movable wall, a cylinder in which the walloperates, a power plunger means connected to said wall, a power plungerchamber, a connection on the power unit adapted to be connected to asource of pressure diiering from the atmospheric pressure, valve means,including `an air valve and a valve, for controlling the access of thesaid pressure to the movable wall, and a control piston having an airvent therein for moving said valves located coaxially with regard to themovable wall and concentrically with thev power plunger means aroundsaid axis.

2. A power unit, comprising a movable wall, a cylinder in which the walloperates, a power plunger means connected to said wall, a power plungerchamber, a connection on the power unit adapted to be connected to asource of pressure differing from the atmospheric pressure, valve means,including an air valve and a valve, mounted on said wall, forcontrolling the access of said pressure to the movable wall, and acontrol piston, having an air vent therein, for moving said valveslocated coaxially with regard to the movable wall and concentricallywith the power plunger means around said axis and movable relatively tothe valve means, on the same side of the w-all as the power plunger.

3. A power unit, comprising a movable wall, a cylinder in which the walloperates, a power plunger means connected to said wall, a power plungerchamber, a connection on the power unit adapted to be connected to asource of pressure diiiering from the atmospheric pressure, valve means,including an air valve and a valve, mounted for relative movement onsaid wall, for controlling the access of the said pressure to themovable wall, and a control piston, having an airvent therein, formoving said valves located coaxially with regard to the movable wall andlf2 concentrically with the power plunger means around said axis andmovable relatively to the valve means, on the same side of the wall asthe power plunger.

4. A power unit, comprising a movable wall, a cylinder in which the walloperates, a plurality of power plungers located in balanced relation toone another connected to said wall, a plurality of power plungerchambers, a connection on the power unit adapted to be connected to asource of pressure differing from the atmospheric pressure, valve means,including 4an air valve and a valve for controlling the access of thesaid pressure to the movable wall, and a control piston for moving saidvalves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis.

5. A power unit, comprising a movable wall, a cylinder in which the walloperates, a power plunger means connected to said wall, a power plungerchamber, a connection on the power unit adapted to be connected to asource of pressure diieringfrom the atmospheric pressure, valve means,including an air valve and a valve for controlling the access of thesaid pressure to the movable wall, and a control plunger, having an airvent therein, for moving said valves located coaxially with regard tothe movable wall and concentrically with the power plunger' means aroundsaid axis, said control plunger having a reaction' spring operated bythe movable wall.

6. A power unit, comprising a movable wall, a cylinder in which the walloperates, a plurality of power plungers located in balanced relation toone another connected to said wall, a plurality of power plungerchambers, a connection on the power unit adapted to be connected to lasource of pressure diiering from the atmospheric pressure, valve means,including an air valve and a valve for controlling the access of thesaid pressure to t'he movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis,said control plunger having a reaction spring operated by the movableWall.

'7. A power unit, comprising a movable wall, a cylinder' in which thewall operates, a power plunger means connected to sad wall, a powerplunger chamber, a connection on the power unit adapted to be connectedto a source of pressure diiering from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, and a Control. plunger, having anair vent therein, for moving said valves located coaxially with regardto. the movable wall and concentricallv with the power plunger meansaround said axis. said control plunger having a star-shaped reactionspring operated by the mOi/f able Wall.

8. A power unit, comprising a movable wall, a cylinder in which the walloperates, a plurality of power plungers located in balanced relation toone another connected to said wall. a plurality 0f power nl urleerVchambers, a connection on the power unit adapted to be connected to asource of pressure diiering from the atmospheric pressure, valve means,including an air valve and a valve for controlling the access of thesaid presT sure to the movable wall, and a control plunger, having anair vent therein, for moving said valves located coaxiallywith regard tothe movable wall and concentrically with the location of the power`plungers around said axis, said control plunger having a star-shapedreaction spring operated by the movable wallL 9. A power unit,comprising a movable wall, a cylinder in which the wall operates, apower plunger means connected to said wall, a power plunger chamber, aconnection on the power unit adapted to be connected to a sourcediffering from the atmospheric pressure, valve means, including an airvalve and a valve for controlling the access of said pressure to themovable wall, and a control plunger for moving said valves locatedcoaxially with regard to the movable wall and concentrically with thepower plunger means around said axis, said control plunger having anoutput reaction spring operated by the movable wall and an input controlspring.

l0. A power unit, comprising a movable wall, av cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis,said control plunger having an output reaction spring operated by themovable wall and an input control spring.

1l. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, a control plunger for moving saidvalves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis,and a passageway connecting the plurality of power plunger chambers.

l2. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure diering from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, a control plunger, having acylinder, for moving said valves located coaxially with regard to themovable wall and concentrically with the location of the plungers aroundsaid axis, a passageway connecting the plurality of power plungerchambers, and a valve between the power plunger chambers and the controlplunger cylinder operated by the control plunger. i

13. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality or" power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure; valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with rea gard to the movable wall andconcentrically with the location of the paper plungers around said axis,said valve means being associated with said control plunger.

14. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure diiering from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis,said vaive means being associated with said control plunger and being inthe form of a grommet having flexible inlet and outlet valve elements.

15. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure diiiering from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the location of the power plunger around said axis,said valve means being associated with said control plunger and being inthe form of a rubber grommet havingV exible inlet and outlet valveelements on the inside and outside of the grommet, respectively.

16. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, valvemeans, including an air Vvalve and a valve for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis,said valve means being associated with said control plunger and havingan inlet valve supporting spring yieldable to excessive differences ofpressure so as to open the inlet valve.

17. vA power unit, comprising a movable Wall, a cylinder in which thewall operates, a piuvrality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, valvemeans, including an air valve' and a valve for controlling the access ofthe said pressure to the movable wall, and a' control plunger for movingsaid valves located coaxiallywith regard to the movable wall andconcentrically with the location of the power plungers around said axis,said valve means being associated with said` control plunger and havingan inlet valve supporting spring vyieldable torexcessive diiierencesofpressure so as to open the inlet valve and a control spring onth cn- 15trol plunger for controlling the actuation of the valve means.

18. A power` unit, comprising a movable wall, a cylinder in which thewall operates, a power plunger means connected to said wall, a powerplunger chamber, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, valvemeans, including an air valve and a valve for controlling the access ofthe said pressure to the movable wall, and a control plunger, having anair vent therei for moving said valves located coaxially with regard tothe movable wall and concentrically with the power plunger means aroundsaid axis and having a reaction spring movable with said wall inopposition to the movement of the control plunger.

19. A power unit, comprising a movable wall, a cylinder in which thewall operates, a power plunger means connected tosaid wall, a powerplunger chamber, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, valvemeans, including an air Valve and a valve for controlling the access ofthe said pressure to the movable wal-l, and a control plunger, having anair vent therein, for movi-ng said valves located coaxially with regardto the movable wall and concentrically with the plunger means aroundsaid axis and having a reaction spring, on which the power plunger meansis mounted, movable with said wal-l in opposition to the movement of thecontrol plunger.

l20. A powerunit, comprising a movable wall, a cylinder which the walloperates, a power plunger means-connected to said wall, a power plungerchamber, a connection on the power adapted tofbe connected to a sourceof pressure diiering from the atmospheric pressure, valve means,including an air valve and a valve for controlling the access of thesaid pressure to the movable wall', andl a control plunger, having anair vent' therein, for moving said valves located coaxially' with regardto the movable Wall and concentrical-ly with the power plunger meansaround saidfaxi's and having a reaction spring, on which the power'plunger means is mounted, movable withv said wall in opposition to themovement ofthe control plunger and a valve control spring on the controlplunger and connected to the reaction-spring.

21. A power unit, comprisinga. mov-able wall', a cylinder in which thewalloperates, apower plunger means comprised of two plungers equidistantfromthe center of and connected to said wall, a power plunger chamber,-a connection on the power unit adapted to be connected to a source ofpressure dii-feringfrom the atmospheric pressure, a valve means,including an air valve and a valve, for controlling the` access of thesaid pressure' to the movable wall, and

moving said valves 'located' coaxially with regard to the movable walland concentrically with the power plunger means around said axis, saidcontrol plunger having an output reaction spring operated by the movablewall, an input control spring exerting force from the control plunger onthe power plunger, and a stop plate for the control spring on thecontrol plunger.

23. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, a valvemeans, including an air valve and a valve, for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically withv the location of the power plungers around saidaxis, said control plunger having an output reaction spring operated bythe movable wall, an input control spring exerting force from thecontrol plunger on the power plunger, and a stop plate for the controlspring on the control plunger.

24. A power unit, comprising a movable wall, a cylinder in which thewall operates, a power plunger means connected to said wall, a powerplunger chamber, a connection on the power unit adapted to be connectedto a source of pressure differing from the atmospheric pressure, a valvemeans, including an air valve and a valve, for controlling the access ofthe said pressure to the movable wall, and a control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the power plunger means around said axis, saidcontrol plunger having an output re ction spring operated by the movablewall, an input control spring exerting force from the control plunger onthe power plunger, and a stop plate for the control spring and reactionspring on the control plunger.

25. A power unit, comprising a movable wall, a cylinder in which thewall operates, a plurality of power plungers located in balancedrelation to one another connected to said wall, a plurality of powerplunger chambers, a connection on the power unit adapted to be connectedto a source of pressure differing from `the atmospheric pressure, valvemeans, including an air valve and a Valve, for controlling the access ofthe said pressure to the movable wall, and a `control plunger for movingsaid valves located coaxially with regard to the movable wall andconcentrically with the location of the power plungers around said axis,said control plunger having an output reaction spring operated by themovable wall, an input control spring exerting force from the controlplunger on the power plunger, and a stop. plate. for the control springand reaction spring on the control plunger.

EDWARD A. ROCKWELL.

' liefert-mes case in the fue of this. patent UNITED STATES PATENTSNumber Name Date 1,781,868 Bragg Nov. 18, 1930 2,275,697 Stelzer Mar.10,A 1942 2,289,043. Rockwellv July 7, 1942 2,308,460 Stelzer Jan. 12,1943 2,359,687 Stelzer Oct. 3, 1944

